In the furniture and cabinet building trade, it is often necessary to utilize a three-way clamp in order to clamp a relatively small workpiece to a larger workpiece. For instance, it is often necessary to clamp a section of molding to the edge of a section of desktop or counter top while the molding is being secured, either with a mechanical fastener or an adhesive such as epoxy, to the larger workpiece. Typically, the artisan, or builder would utilize a traditional, state of the art three-way clamp. With the traditional three-way clamp, two of the work heads, are biased towards each other and towards the upper and lower surfaces of the larger workpiece. This linear, unidirectional force provides a stabile base against which the third workhead applies a second linear, unidirectional force which biases the smaller workpiece against the edge of the larger workpiece. However, there are at least two problems associated with using the traditional three-way clamp in this manner: one, each workhead must be individually manipulated in order to apply the linear, unidirectional force against the workpieces; and two, the two opposing linear, unidirectional forces must be set first, after which the third force is set, however, depending upon the surface and surface area of the two opposing workheads, the force necessary to overcome the frictional force between the opposing workheads and the surface of the large workpiece may be less than the second linear force applied by the third workpiece. The result is that the third workpiece actually forces the clamp off of the workpieces. Various clamping devices are known in the art: For instance, U.S. Pat. No. 3,590,669, issued to Marasco, on Jul. 6, 1971 discloses improved pliers with a toggle-type grip lock. U.S. Pat. No. 3,578,307, issued to Lock, on May 11, 1971, discloses an improved "Stilson"-type pipe wrench. U.S. Pat. No. 3,718,327, issued to Nunez, on Feb. 27, 1973, discloses a portable vice formed from a c-clamp that has been adapted for rigid mounting to a structural member and that is provided with auxiliary clamp means that cooperate with the c-clamp. U.S. Pat. No. 3,807,718, issued to Sendoykas, on Apr. 30, 1974, discloses a novel linkage assembly for toggle actuated clamping devices. U.S. Des. Pat. No. Des. 269,476, issued to Knaus, on Sep. 1, 1981, discloses an ornamental design for a combined locking pliers clamp. And, U.S. Pat. No. 4,795,141, issued to Mulvaney, on Jan. 3, 1989, discloses a cam locked fixture for stabilizing the position of a stud during nailing.
What is heretofore missing from the art is a locking three-way clamp that provides the ease of adjustment of the traditional locking pliers while applying a vector force that has both horizontal and vertical component vectors that bias the clamp against two workpieces rather than working to force the clamp off of the workpiece.
Accordingly, it is an object of the present invention to provide a locking clamp that includes a workpiece restraint member and an engagement device which pivots inward towards the restraint member thus applying a vector force having a component vector towards the workpiece and a component vector towards the restraint member.
Another object of the present invention is to provide a locking clamp in which the engagement device is defined by a pair of opposing, eccentrically mounted cams.
A further object of the present invention is to provide a locking clamp in which the engagement device is defined by a pair of linkages pivotally secured to the jaws of the clamp, each linkage including a pivotally mounted workhead.
Other objects and advantages over the prior art will become apparent to those skilled in the art upon reading the detailed description together with the drawings as described as follows.